Secret telegraph receiver



Aug; 13, 1935. F. L. CURRIE 2,011,145

SECRET TELEGRAH RECE IVER Filed Sept. 9, 1933 ,wan/75 raf/15'@ Patented Aug. 13, 1935 Western Union Telegraph Company,

New

York, N. Y., a corporation of New York Application September 9, 1933, Serial No. 688,848

4 Claims.

This invention relates to telegraph receivers and particularly to silent Sounders or receiving instruments by means of which messages may be received without depending upon the usual audible signals. It is intended primarily for use in those places where the noise ci the ordinary sounder is objectionable.

The ordinary telephone receiver has been used as a telegraphic receiver either connected directly in circuit with the sounder or in a local circuit c controlled by the contacts of a telegraph relay.

Receiving Sounders of telegraph single current sets are normally adjusted so that a distinct contrast exists between the sounds produced by the downward and the upward movement of the sounder lever in response to the make and break operations of the relay contacts. Telegraph operators nd that this contrast is a decided assistance in the reading or the Morse characters. For the purpose of emulating this contrast it has been proposed to actuate the telephone receiver by means of a local circuit including a microphone responsive to sounds emanating from a telegraph sounder, the microphone being tuned particularly to the sound of the lever striking the anvil for a make in the telegraph circuit.

My invention provides for the actuation of the telephone receiver under the direct control of the relay contacts, the contrast between the make andbreak operations being effected by means of a time-lag element which controls the rate of decrease of the local circuit current from a maximum to a minimum Value when the relay contacts are separated.

The particular means that I may employ to secure the time-lag eiect will now be described in connection with the accompanying drawing which illustrates one embodiment of the invention. It is to be understood that I do not intend to be limited to the precise details shown or described except as the same are set out in the accompanying claims.

In carrying out my invention I connect a standard telephone receiver i, in a local circuit, including a battery 2, and adjustable resistance 3, to the front contact fi and armature 5 of the usual telegraph relay 6. In shunt to said contact and armature I connect an adjustable condenser 1. When the relay armature engages its front contact in response to a signal impulse, the

telephone receiver will respond to current from battery 2 with a quick sharp click, the condenser 'l being short-circuited at the contact 4. When the .armature 5 is retracted in response to a break telegraph signal, a charging current will iiow from the battery 2 into the condenser in accordance with the Well known exponential law. Inasmuch as the intensity of sound in a telephone receiver is dependent upon the rate of change of the current iiowing through its windings, it will be apparent that the sounds produced in the telephone receiver will differ lin intensity in a manner to clearly distinguish between the make and break operations of the relay. The capacity of the condenser may be adjusted to produce the proper time-lag in the local circuit so that the rate of change of the current from a maximum to a minimum produces the desired contrast in so'und in the telephone receiver in response to the make and break operations of the relay.

I claim:-

1. In combination, a telegraph relay, a telephone receiver, a circuit including said receiver and a source of current adapted tol be closed and opened by the operation ofthe contacts of said relay and a'time-lag element controlling the flow of current in said circuit only upon the opening of said contacts.

2. In combination, a telegraph relay, a telephone receiver, a circuit including said receiver and a source of current adapted to be closed and opened by the operation of the contacts of said relay and a condenser connected in par-allel to said relay contacts only when the contacts are separated.

3. In combination, a telegraph circuit having means adapted to make and break the current therein, a telephone receiver, means tocause said receiver to respond to the makes and breaks in said circuit, and a time-lag element operating to delay the rate of change of current flowing in the receiver only during response to said breaks.

4. In combination, a telegraph circuit having means to make and break the current therein, a telephone receiver operating in a local circuit, a condenser connected to said circuit, means to cause said receiver to respond to the makes and breaks in said circuit, said means operating to short circuit said condenser during the make operations..

FRANK L. CURRIE. 

